A reactive oxygen species burst causes haploid induction in maize

Haploid induction (HI) is an important tool in crop breeding. Phospholipase A1 (ZmPLA1)/NOT LIKE DAD (NLD)/MATRILINEAL (MTL) is a key gene controlling HI in maize;however, the underlying molecular mechanism remains unclear. In this study, to dissect why loss of ZmPLA1 function could mediate HI we performed a comprehensive multiple omics analysis of zmpla1 mutant anthers by integrating transcriptome, metabolome, quantitative proteome, and protein modification data. Functional classes of significantly enriched or differentially abundant molecular entities were found to be associated with the oxidative stress response, suggesting that a reactive oxygen species (ROS) burst plays a critical role in HI. In support of this, we further discovered that a simple chemical treatment of pollen with ROS reagents could lead to HI. Moreover, we identified ZmPOD65, which encodes a sperm-specific peroxidase, as a new gene controlling HI. Taken together, our study revealed a likely mechanism of HI, discovered a new gene controlling HI, and created a new method for HI in maize, indicating the importance of ROS balance in maintaining normal reproduction and providing a potential route to accelerate crop breeding.

A novel protein complex that regulates active DNA demethylation in Arabidopsis

Active DNA demethylation is critical for altering DNA methylation patterns and regulating gene expression.The 5-methylcytosine DNA glycosylase/lyase ROS1 initiates a base-excision repair pathway for active DNA demethylation and is required for the prevention of DNA hypermethylation at 1000 s of genomic regions in Arabidopsis.How ROS1 is regulated and targeted to specific genomic regions is not well understood.Here,we report the discovery of an Arabidopsis protein complex that contains ROS1,regulates ROS1 gene expression,and likely targets the ROS1 protein to specific genomic regions.ROS1 physically interacts with a WD40 domain protein(RWD40),which in turn interacts with a methyl-DNA binding protein(RMB1)as well as with a zinc finger and homeobox domain protein(RHD1).RMB1 binds to DNA that is methylated in any sequence context,and this binding is necessary for its function in vivo.Loss-of-function mutations in RWD40,RMB1,or RHD1 cause DNA hypermethylation at several tested genomic regions independently of the known ROS1 regulator IDM1.Because the hypermethylated genomic regions include the DNA methylation monitoring sequence in the ROS1 promoter,plants mutated in RWD40,RMB1,or RHD1 show increased ROS1 expression.Importantly,ROS1 binding to the ROS1 promoter requires RWD40,RMB1,and RHD1,suggesting that this complex dictates ROS1 targeting to this locus.Our results demonstrate that ROS1 forms a protein complex with RWD40,RMB1,and RHD1,and that this novel complex regulates active DNA demethylation at several endogenous loci in Arabidopsis.

SWO1 modulates cell wall integrity under salt stress by interacting with importinɑin Arabidopsis

Maintenance of cell wall integrity is of great importance not only for plant growth and development,but also for the adaptation of plants to adverse environments.However,how the cell wall integrity is modulated under salt stress is still poorly understood.Here,we report that a nuclear-localized Agenet domain-containing protein SWO1(SWOLLEN 1)is required for the maintenance of cell wall integrity in Arabidopsis under salt stress.Mutation in SWO1 gene results in swollen root tips,disordered root cell morphology,and root elongation inhibition under salt stress.The swo1 mutant accumulates less cellulose and pectin but more lignin under high salinity.RNA-seq and ChIP-seq assays reveal that SWO1 binds to the promoter of several cell wall-related genes and regulates their expression under saline conditions.Further study indicates that SWO1 interacts with importinɑIMPA1 and IMPA2,which are required for the import of nuclear-localized proteins.The impa1 impa2 double mutant also exhibits root growth inhibition under salt stress and mutations of these two genes aggravate the salt-hypersensitive phenotype of the swo1 mutant.Taken together,our data suggest that SWO1 functions together with importinɑto regulate the expression of cell wall-related genes,which enables plants to maintain cell wall integrity under high salinity.